A negative glow discharge lamp typically comprises a light-transmitting envelope, which contains a noble gas and mercury (Hg) with a phosphor coating on the inner surface of the envelope. This coating enables the emission of visible light upon absorption of ultraviolet radiation that occurs when the electrical circuit is activated and ultraviolet radiation is emitted. The phosphor coating absorbs the emitted ultraviolet radiation. Examples of typical glow discharge lamps are found in U.S. Pat. No. 2,067,129 to Marden; U.S. Pat. No. 3,814,971 to Bhattacharya; U.S. Pat. No. 4,408,141 to Byszewski, et.al., and U.S. Pat. No. 4,751,435 to Roche, et.al. Such lamps can be operated from either an AC or DC power source.
Various attempts have been made to produce fluorescent lamps with bulb bases whereby the lamps may be mounted into standard screw-type sockets. In such arrangements the starting circuit for such lamps must be located some place in the lamp. In U.S. Pat. No. 4,688,874 to Bjorkman it has been suggested to provide an adapter which has a screw base and a holder to receive the fluorescent lamp. The adapter carries such ignition and drive circuitry.
In U.S. Pat. No. 4,871,944 to Skwirut et.al., a screw-in type base fluorescent lamp is shown which contains a tridimensional convoluted tubular envelop and circuit elements within the lamp unit.
In U.S. Pat. No. 4,644,224 to Saita et.al., there is disclosed a low pressure mercury vapor discharge lamp in which a starting circuit is enclosed in a separate case mounted above a screw-in bulb case and to which in turn a glass lamp envelope is mounted.
In all such devices, the resultant lamp is unacceptably lengthened or the structure employed makes the lamp unit impractical from a commercial standpoint.